Fusion protein of vhh antibody and streptavidin mutant

Abstract

A fusion protein of a molecule that recognizes cancer cells or the like and a mutant streptavidin, wherein the fusion protein is for use in the treatment or diagnosis of a cancer, is provided. In the fusion protein, a VHH antibody is bound, via a linker sequence, to the N-terminal side and/or C-terminal side of the amino acid sequence as set forth in SEQ ID NO: 1, provided that the C-terminal amino acid sequence consisting of Pro-Ser-Ala-Ala-Ser-His-His-His-His-His-His may be partially or entirely deleted.

1 . A fusion protein, wherein a VHH antibody is bound, via a linker sequence, to the N-terminal side and/or C-terminal side of the amino acid sequence as set forth in SEQ ID NO: 1, provided that the C-terminal amino acid sequence consisting of Pro-Ser-Ala-Ala-Ser-His-His-His-His-His-His may be partially or entirely deleted. 
     
     
         2 . The fusion protein according to  claim 1 , which has the VHH antibody, the linker sequence, and the amino acid sequence as set forth in SEQ ID NO: 1, provided that the C-terminal amino acid sequence consisting of Pro-Ser-Ala-Ala-Ser-His-His-His-His-His-His may be partially or entirely deleted, in this order from the N-terminal side to the C-terminal side. 
     
     
         3 . The fusion protein according to  claim 1 , wherein the VHH antibody is an antibody that binds to an antigen expressing in a cancer cell. 
     
     
         4 . The fusion protein according to  claim 1 , wherein the VHH antibody is an antibody that binds to Her2. 
     
     
         5 . The fusion protein according to  claim 1 , wherein the VHH antibody has the amino acid sequence as set forth in SEQ ID NO: 2. 
     
     
         6 . The fusion protein according to  claim 1 , wherein the linker sequence consists of a glycine residue(s) and a serine residue(s) and the number of the amino acid residues is 5 to 25. 
     
     
         7 . The fusion protein according to  claim 1 , wherein the linker sequence is an amino acid sequence represented by [(Gly) m -Ser] n  wherein m represents an integer of 1 to 10, and n represents an integer of 1 to 5. 
     
     
         8 . The fusion protein according to  claim 1 , which has the amino acid sequence as set forth in SEQ ID NO: 3, provided that the C-terminal amino acid sequence consisting of Pro-Ser-Ala-Ala-Ser-His-His-His-His-His-His may be partially or entirely deleted. 
     
     
         9 . A nucleic acid encoding the fusion protein having the amino acid sequence as set forth in SEQ ID NO: 3, provided that the C-terminal amino acid sequence consisting of Pro-Ser-Ala-Ala-Ser-His-His-His-His-His-His may be partially or entirely deleted. 
     
     
         10 . A cancer therapeutic agent or a cancer diagnostic agent, comprising the fusion protein according to  claim 1 . 
     
     
         11 . A kit for treating or diagnosing cancer, comprising (1) the fusion protein according to  claim 1 , and (2) a conjugate of a compound represented by the following formula (1) or a salt thereof, and a diagnostic substance or a therapeutic substance: 
       
         
           
           
               
               
           
         
         wherein 
         X1a, X1b, X2a and X2b each independently represent O or NH, 
         Y 1  and Y 2  each independently represent C or S, 
         Z 1  and Z 2  each independently represent O, S or NH, 
         V 1  and V 2  each independently represent S or S + —O − , n1 and n2 each independently represent an integer of 0 or 1, 
         L 1  and L 2  each independently represent a divalent linking group, 
         L 3  represents a group comprising a functional group capable of binding to the diagnostic substance or the therapeutic substance at the terminus thereof, and 
         L 4  represents a trivalent linking group. 
       
     
     
         12 . The kit according to  claim 11 , wherein the diagnostic substance or the therapeutic substance is a phthalocyanine dye or an anti-cancer drug. 
     
     
         13 . A method for producing the fusion protein according to  claim 1 , comprising
 allowing a nucleic acid encoding the fusion protein to express in a host.   
     
     
         14 . The method according to  claim 13 , wherein the fusion protein is allowed to express in a bacterial inclusion body and is then recovered.